Host castration by Aphidius ervi venom proteins.

Area of Science:

• Entomology
• Insect Physiology
• Chemical Ecology

Background:

• Aphidius ervi is an endoparasitoid of the pea aphid, Acyrthosiphon pisum.
• Parasitization by A. ervi leads to host aphid castration, particularly when oviposition occurs in early instars.
• Deleterious effects on the host reproductive system are observed within 24 hours of parasitization, prior to embryonic development.

Purpose of the Study:

• To investigate the effect of A. ervi venom on A. pisum ovaries.
• To identify the cellular alterations induced by venom components.
• To characterize the bioactive molecules responsible for host reproductive damage.

Main Methods:

• Microinjection of A. ervi venom into non-parasitized A. pisum.
• Observation of cellular alterations in the apical germaria of ovarioles using electron microscopy.
• Biochemical analysis of venom components, including heat and protease sensitivity assays and protein purification.

Main Results:

• Venom microinjection replicated the ovarian alterations observed in parasitized aphids.
• Germarial cells in venom-treated and parasitized aphids lacked nucleoli and nuage material by 24 hours.
• Degenerative signs, possibly apoptosis, were evident by 48 hours.
• The active venom component was heat- and protease-sensitive, associated with two non-glycosylated proteins (21kD and 36kD).

Conclusions:

• A. ervi venom directly induces ovarian damage and castration in A. pisum.
• The venom's bioactive components are heat- and protease-sensitive proteins, likely responsible for inducing apoptosis.
• These findings shed light on the mechanisms of venom action in parasitic wasps and their impact on host reproduction.